This invention relates to medical tissue expansion, and more particularly it pertains to a prostatic tissue expander balloon catheter for expanding the prostatic urethra over a period of time. Inflation balloon pressure is maintained by valves in the inflation lumens. The tissue expander catheter is used to expand the prostatic urethra for the treatment of BPH (Benign Prostatic Hypertrophy).
By far the most common prostate problem is enlargement of the gland, or BPH. Common in men over 50, it is simply excess growth in the innermost part of the prostate. The urethra that empties the bladder runs through the middle of the prostate. The more the prostate enlarges, the more the flow of urine is constricted, causing a variety of uncomfortable symptoms when one tries to urinate.
The surgical solution to prostate enlargement has become the most common surgery confronting adult males today. It is known as Transurethral Resection of the Prostate (TURP). The Transurethral Resection procedure is carried out through a narrow tube-like instrument called a resectoscope, which is inserted into the urinary canal via the penis. Working through the resectoscope, the urologist carves out a portion of the prostate to enlarge the urinary passageway.
A recent alternative to TURP prostate surgery is the use of a small balloon, temporarily inserted into the urinary canal, precisely positioned where the urethra passes through the prostate, then inflated (for just minutes usually) to enlarge the urinary passageway where it is constricted by the enlarged prostate. During the 1980's, this concept in a different procedure won wide acceptance among cardiologists, who use a tiny balloon catheter to enlarge clogged blood vessels through a procedure called "angioplasty". In the case of the prostate, the procedure is known as "transcystoscopic urethroplasty". It is the urethra (not an artery) that is blocked, and it is the flow of urine (not blood) that is obstructed.
The Optilume Prostate Balloon Dilator manufactured by American Medical Systems is a dilator of the foregoing type for use in transcystoscopic urethroplasty. It has a non-distensible, single size, dilation balloon (diameter: 30 mm [90 Fr], length: 80 mm) located near the tip of a catheter shaft. A transparent locating balloon is mounted proximal to the dilation balloon. The balloons are enclosed in a PTFE sheath for placement in the urethra. This type of dilator is more fully described in U.S. Pat. Nos. 4,932,956 and 4,932,958 to Ready.
The sheath enclosed catheter of the dilator is inserted into the urethra. The balloons are moved out of the sheath and into working position with the locating balloon in the bulbous urethra, resting against the external sphincter. Positioning is accomplished by palpation, fluoroscopy or by placing a rod lens along side of the PTFE sheath and looking through the transparent locating balloon to confirm that the dilation balloon is in the proper location. The dilation balloon is inflated up to 60 PSI for 10 to 15 minutes, after which both balloons are deflated. The catheter is then drawn back into the sheath and removed.
In order to improve the removal characteristics, and thereby increase patient comfort, the dilator utilizes a PET balloon design which has a layer of silicone over the PET balloon with a coating of lubricant between the layers. The smooth finish and the elastic properties of the silicone permit easier removal of the deflated balloon.
Another known device is the Dowd catheter manufactured by Microvasive, Inc., which also has a non-distensible dilation balloon measuring 30 mm in diameter and 85 mm in length. A palpation nodule is mounted proximal of the balloon near the proximal end of the shaft. A knob is affixed to the shaft to provide a means of maintaining the position of the balloon during inflation. In use, the Dowd catheter is manually inserted without benefit of introducers or other sheaths. Throughout the entire procedure, the physician has a finger in the rectum against the nodule to judge positioning of the catheter. The balloon is inflated up to 60 PSI for the duration of the 10 to 15 minute procedure. During this time the urologist must maintain traction of the shaft to prevent the balloon from migrating into the bladder. The balloon is removed following deflation by twisting and pulling.
Another known device is the Uroplasty TCU design manufactured by Advanced Surgical Intervention. It features a Foley Balloon at its distal tip and a non-distensible dilation balloon mounted just proximal to the Foley balloon. The dilation balloon has a diameter of 25 mm (75 Fr), and is available in lengths from 15 mm to 55 mm.
A special "calibration" catheter with distance graduations on its shaft is inserted through a disposable introducer sheath which contains a rod lens for viewing the graduation adjacent to the sphincter. The calibration catheter is removed and a dilation catheter having the proper length balloon is installed. The Foley balloon on the dilation catheter is inflated in the bladder and exact placement is confirmed through the lens. The dilation balloon is inflated at up to 45 PSI for 10 to 15 minutes. Migration is not possible because the catheter is anchored by having one balloon on each side of the bladder neck. Upon deflation, the balloon is removed by withdrawing it through the introducer sheath thereby preventing further trauma to the urethra. Rosenbluth, U.S. Pat. Nos. 5,007,898 and 5,030,227, and Klein U.S. Pat. Nos. 4,660,560 and 5,002,558 describe such devices and are incorporated herein by reference in their entirety.
Balloon dilation of the prostatic urethra may produce a commissurotomy or tearing, which is considered by some to enhance the results. Bleeding frequently accompanies the procedure. A catheter may be placed immediately following the dilation to allow the patient to void comfortably. Unfortunately, it has been found that the beneficial results from treatment as mentioned above are fairly short lived for the balloon dilation procedure.
As noted above, transcystoscopic urethroplasty (TCU) or transurethral balloon dilation of the prostate (TUDP) can and in many cases does rupture the urethra (commissurotomy). Even so, the progressive development of this technique has tended toward the use of larger and larger diameter dilation balloons. See the paper entitled "Dilation of the Prostatic Urethra with 35 mm Balloon" by McLaughlin et al., which appeared in the BRITISH JOURNAL OF UROLOGY (1991), 67, 177-181.
A procedure known as tissue expansion is also known in the medical art. In tissue expansion procedures, a temporary device for expanding or stretching skin and tissue is placed within the body and is expanded over an extended period of time and left in place until the tissue or skin stabilizes to an enlarged and permanent size. This procedure is used to treat burn victims and for breast reconstruction. See U.S. Pat. Nos. 4,643,733 and 4,217,889 for example. No one to date has thought to apply the concept of tissue expansion to the TCU or TUDP procedure, utilizing a distensible balloon, as a substitute for the presently practiced procedure utilizing short time balloon dilation with a non-distensible balloon.